1. Field of the Invention
The present invention relates to an optical switch and a switching method thereof for switching of optical transmission lines consisting of optical fibers, for example, in the field of optical communication.
2. Related Background Art
An example of such optical switch known heretofore is the apparatus of the type disclosed in the bulletin of Japanese Laid-open Patent Application No. Hei 6-67101. This optical switch has a first optical fiber group composed of a number of first optical fibers, an optical fiber arraying member for arraying the first optical fiber group horizontally, a second optical fiber, an optical fiber driving mechanism for holding this second optical fiber and mechanically moving the second optical fiber to optically couple the second optical fiber with an arbitrary first optical fiber, and a sealing case for housing the first optical fiber group, second optical fiber, optical fiber arraying member, and optical fiber driving mechanism. The sealing case is filled with an index matching agent having an index of refraction nearly equal to that of the first optical fibers and second optical fiber, such as silicone oil. Therefore, the index matching agent is interposed in a gap between connected end faces of the first optical fiber and second optical fiber, which decreases optical losses due to scattering or the like in this gap, which prevents optical loss build up due to switching of the first optical fiber and second optical fiber, and which stabilizes optical characteristics.
This conventional, optical switch, however, had the following problems because of the above-stated structure.
Specifically, since the optical switch was constructed in the structure wherein the optical fiber driving mechanism was immersed in the index matching agent, foreign matter such as wear powder produced by mechanical contact or abrasion of the optical fiber driving mechanism flowed into the index matching agent filling the case and moved therein to intrude into the coupling part between the optical fibers, which resulted in degrading the optical characteristics of optical switch. Since the silicone oil used as an index matching agent is likely to leak even through a fine hole, the oil seal structure was complex in the sealing case (taking countermeasures against leakage, countermeasures during the assembling step, etc.).
An object of the present invention is to provide an optical switch that is unlikely to experience the deterioration of optical characteristics due to intrusion of foreign matter into the coupling part between optical fibers and that requires no complex seal structure, solving the above problems.